As in past milestones for the iTunes Music Store, Apple has announced a contest for the leadup to the 1 billionth download.

There will be prizes awarded for every 100,000 song milestone starting at 950,100,000 including a black 4GB iPod nano & a $100 iTunes Music Card.

The grand prize winner who downloads the 1 billionth song will receive 1 20-inch iMac, 10 60GB iPods (5 white, 5 black) and a $10,000 iTunes Music Card.

You will have to search google for more info on this since ebay will not allow links within guides. 

Good Luck!